44 SCIENTIFIC HORSESHOEING. 



the cutigeral cavity, at the upper border of the horny wall, 

 and forms a rounded prominence of dense, thick fibers, and 

 assists in the elastic action of the cartilages and laminar tissues. 

 Its surface is tufted with villi and shows a considerable number 

 of nerves and blood-vessels which branch throuo'h its sub- 

 stance and secrete the horny tissue of the wall. Around its 

 upper border is a narrow, lip-like margin called the perioplic 

 ring, from which exudes the periople — the natural horny var- 

 nish of the wall. The coronarv cushion mino;les with the in- 

 ternal tissues of the foot and becomes continuous with the 

 bulbs of the sensitive frog. See colored plates. 



Sensitive Tissues. — The sensitive frog, or plantar cushion, 

 is a thick, wedge-shaped mass of fibrous structure of fine 

 elastic pulp situated beneath and behind the foot bones (to 

 which it is attached) and between the back tendons (which it 

 supports) and the lower part of the hoof. It is lodged in the 

 fissures of the horny frog, receiving the spur or frog stay in the 

 middle of its pyramidal body, which thus divides it into two 

 diverging bulbs exactly like that of the outer frog to which it 

 corresponds. At the point, or apex in front, it becomes con- 

 tinuous with the sensitive sole, and at the sides is attached to 

 the lower edges of the cartilages. The base, formed by the 

 bulbs behind, is inclined upward, and mixes its fibers with the 

 cartilages and coronary cushion. Numerous blood-vessels and 

 nerves complete this structure. See colored plates. 



The sensitive sole, or velvety tissue, is the formative organ of 

 the horny sole and frog. It is much thinner than the plantar 

 cushion, and extends over or under the entire plantar region as 

 well as the plantar cushion, which it covers by adapting itself 

 to the inequalities of this elastic mass. This tissue shows the 

 same structure as the coronary cushion, with the extremities of 

 which it unites on the bulbs of the frog continuing above the 

 laminpe on the bars. The surface of this tissue is studded with 



